Frequency Domain Analysis of the Influence of Compensating Wires and Earthing Resistances in Mixed Overhead / Underground HV Transmission Lines

摘要

In the framework of the Randstad380 project, the Dutch 380 kV transmission system is being extended. The new connection comprises underground power cables connected by an overhead line (OHL), special pylon design, and use of compensating wires. To accurately model this connection with all mutually coupled conductors (e.g. in total 26 underground), cross-bonded sections, different trench types, and to thoroughly investigate the effect of each parameters on electromagnetic transients behaviour, a frequency-domain approach is adopted which can be tailored to efficiently analyse power system transients for this connection. The method is applied to analyse the influence of compensating wires and earthing resistances in the both OHL and cable connections on resonant behaviour up to 10 kHz. Results for per unit length capacitances, DC resistances, positive- and zero-sequence impedances of the overhead lines and cables results are compared with measurements as well as with PSCAD/EMTDC simulations made for a simplified configuration. It is found that the compensating wires have mainly influence in the nearby area and at higher frequencies. The sensitivity of all transfer functions related to the voltages and currents at both terminals of the transmission line to the compensation wires and earthing resistances are investigated. Generally, within the frequency range up to 10 kHz, the transfer functions are not much influenced by compensating wires except for resonances in transfer functions above about 3 kHz which are shifted to higher frequencies. Earthing resistances mainly affect the damping of resonances.